The aim was to evaluate the replacement of soybean meal by inactive dry yeast (Saccharomyces cerevisiae) from sugar cane on nutritive value of diets for Saanen goats in the peripartum. Twenty-four Saanen goats (nine primiparous, 55.35 ± 4.55 kg and fifteen multiparous, 73.12 ± 8.51 kg) in prepartum and postpartum periods were distributed in a completely randomized design with a 3 × 2 (diet × parturition order) factorial arrangement. Diets were composed of soybean meal, soybean meal plus dry yeast or dry yeast as protein source, and other ingredients: ground corn, mineral supplement and limestone. The roughage source used was the whole plant corn silage (40% of the total diet). Diets were evaluated as dry matter intake and digestibility of nutrients. The diet with total dry yeast inclusion promoted a reduction on the ether extract intake (postpartum) and ether extract digestibility (prepartum and postpartum), due its lower ether extract content when compared to the other diets. Multiparous goats presented higher intakes for dry matter, nutrients and total digestible nutrients in both evaluated periods due their higher intake capacity. Primiparous goats in postpartum had better coefficients of digestibility for dry matter, organic matter, crude protein and total carbohydrates, and so a higher energetic value, attributed to total digestible nutrients compared to multiparous ones. Dry yeast can replace soybean meal with no changes on nutritive value of diets for Saanen goats.

Late pregnancy and early lactation correspond to a period during which intense metabolic and physiologic changes occur in females. At the end of pregnancy, the compression of the rumen by fetal growth and the action of some hormones involved in homeorhesis reduces feed intake capacity (RODRIGUES et al., 2006). This reduction can impair meeting nutrient requirements, which can modify physiologic mechanisms of body store mobilization and cause metabolic disturbances after calving (RODRIGUES et al., 2007).

Inactive dry yeast from sugar cane (Saccharomyces cerevisiae) is used in animal feeding mainly due its protein content, about 42% (BUTOLO, 2010). It has also a good amino acid profile, and large amounts of B-vitamins and minerals such as zinc and selenium (AMORIM; LOPES, 2009).

This study was performed to evaluate the replacement of soybean meal by inactive dry yeast (Saccharomyces cerevisiae) from sugar cane on nutritive value of diets for primiparous and multiparous Saanen goats during prepartum and postpartum periods.

MATERIAL AND METHODS

The experiment was carried out at Fazenda Experimental de Iguatemi, of the Universidade Estadual de Maringá, Paraná, Brazil. Nine primiparous (55.35 ± 4.55 kg) and 15 multiparous (73.12 ± 8.51 kg) Saanen goats were assigned to a completely randomized design with a 3 × 2 (diet × parturition order) factorial arrangement of treatments. Goats were weighed at the beginning of the study and weekly afterward.

1Corn silage, ground corn and soybean meal were estimated from values of degradable protein recommended by the NRC (2007); for dry yeast, degradable protein was estimated from 80% of crude protein, once 20% total nitrogen may be nucleic acids (AMORIM; LOPES, 2009).

Goats were housed in individual stalls with free access to water. Fresh feed was provided twice daily at 0930 and 1600 h and approximately 100 g/kg were allowed in orts. The supplied feeds and orts were weighed daily to calculate voluntary intake. After kidding, the goats were milked at 0730 and 1500 h.

Due to differences between the predicted and actual kidding dates, prepartum and postpartum data collection began 10 days before and ended 10 days after kidding, respectively, in order to include a complete sample of goats for all the observational days. Feed intake was recorded daily and samples of TMD and orts were taken at -10 to -5 days (before partum) and +10 to +15 days (after partum) in each collection period, and pooled by goat within each period (prepartum and postpartum). Apparent total tract digestibility was evaluated over 6 days in each collection period. Samples of feces were collected from the exit of the rectum on consecutive days at 0800; 1000; 1200; 1400; 1600 and 1800 h, respectively. All samples were frozen at -20ºC for subsequent drying at 55ºC, and ground through a 1 mm screen in a Wiley mill for further analyses.

Indigestible NDF (iNDF) was used as a marker to estimate fecal output and digestibility. Analysis of iNDF was performed by 144 hours of in situ (in rumen fistulated goats) incubation of diets, orts and feces within nylon bags (F57 Ankom) followed by neutral detergent analysis (MERTENS, 2002) by an Ankom200 Fiber Analyzer (Ankom Technology Corp., Fairport, NY).

The dietary rumen degradable protein (RDP) content was estimated according to NRC (2007). The values considered were 72.50; 42.22 and 64.07% for corn silage, ground corn, and soybean meal, respectively. For dry yeast, 80% of RDP from the crude protein was considered, because about 20% from the nitrogenous content are nucleic acids (AMORIM; LOPES, 2009).

There was no significant diet effect on body weight and intakes of dry matter, organic matter, crude protein, rumen degradable protein, neutral detergent fiber, total carbohydrates or total digestible nutrients for goats on either period (prepartum and postpartum) (Table 3). The observed averages for dry matter intake on prepartum period were 1513.7; 1483.2 and 1538.4 g/day and in the postpartum the averages were 1764.4; 1632.5 and 1660.3 g/day, for diets soybean meal; soybean meal plus dry yeast and dry yeast, respectively, and this suggests that dry yeast and soybean meal have similar acceptability in peripartum goats. Similarly, other studies have shown no effects of dry yeast on dry matter intake in sheep (AGUIAR et al., 2007) and goats (FREITAS et al., 2011; LIMA et al., 2011).

The replacement of soybean meal by dry yeast in the diets reduced (P<0.05) ether extract intake for goats in postpartum period (Table 3). This agrees with the results of LIMA et al. (2012a), who reported that feeding dry yeast as a protein source to lactating goats reduced the ether extract intake compared with soybean meal. The explanation for this effect may be based on the lower ether extract proportion in dry yeast (0.18%) compared to soybean meal (2.9%), likely accounted for the observed reduced ether extract intake.

Parturition order influenced (P<0.05) both prepartum and postpartum body weight, intake of dry matter, nutrients and total digestible nutrients, with multiparous goats showing the highest values (Table 3). Similar results have been reported previously by a study in which two-years-old goats presented a higher intake of dry matter and nutrients compared to one-year-old goats fed diets containing dry yeast (ALCALDE et al., 2010). This suggests that intake is strongly affected by age and parity, since they are related to body development and the full capacity of the rumen. Indeed, some factors, such as fiber content and the energetic density of the diet, nutritional requirements and the ruminal capacity of the animals have been reported to regulate dry matter intake capacity in ruminants (PEREIRA et al., 2003). Thus, the higher dry matter intake observed in multiparous occurred mainly due to their higher relative intake capacity.

In the prepartum period, primiparous consumed about 5% less feed while multiparous consumed about 14% less feed, than in the postpartum. In fact, in the last three weeks before calving a compression of the rumen by the fetus occurs and dry matter intake can be reduced by about 5 to 10% (RIBEIRO, 1997). Also, in early lactation, intake capacity is still critical, until the 7th to 11th week, when dry matter intake is completely restored (GOMES et al., 2014b).

The digestibility of dry matter, organic matter, crude protein, neutral detergent fiber and total carbohydrates were similar among diets during prepartum and postpartum (Table 4).

Table 4: Digestibility of dry matter and nutrients and energetic value of diets in Saanen goats.

Similarly to these results, when castrated Saanen goats were fed portions of dry yeast (0, 25, 50, 75 and 100%) instead of soybean meal, differences in dry matter and nutrient digestibility were not observed (LIMA et al., 2012b). However, the digestibility of dry matter and nutrients can be improved when dry yeast is included in diets for heifers and goat kids, as reported by Martins et al. (2000) and Lima et al. (2011), respectively.

Digestibility is directly influenced by the feed intake, diet composition, degradability, protein to energy ratio and factors related to the animals (VAN SOEST, 1994). So, the reduction (P<0.05) observed in digestibility of the ether extract, is mainly related to the diet composition, diets with dry yeast presented lower ether extract content. Also, Freitas et al. (2011) reported a linear reduction in ether extract digestibility for goat kids with 0, 25, 50, 75 and 100% of dry yeast included in the diets, due to the minimal ether extract content in dry yeast (0.32%). Lima et al. (2012b) observed a reduction of ether extract digestibility from the inclusion of 38.5% of dry yeast in diets for Saanen goats.

Although ether extract digestibility was reduced (P<0.05) by the inclusion of dry yeast in the diets, the results for total digestible nutrients, in prepartum and postpartum, were not affected. Also, no difference was observed in total digestible nutrients, when soybean meal was replaced by dry yeast (LIMA et al., 2012b). These results may be related mainly to the similar digestibility of crude protein and total carbohydrates observed among the diets (Table 4). The inclusion of dry yeast in diets provided good energetic value for goats; expressed by the following overall averages obtained for total digestible nutrients 742.1 and 773.6 g/kg, in prepartum and postpartum periods, respectively.

Parturition order did not influence the digestibility of dry matter and nutrients in the prepartum period, however, in postpartum, primiparous goats presented better digestibility for dry matter organic matter, crude protein and total carbohydrates. So, in postpartum, a higher energetic value of the diets, was observed for primiparous than for multiparous goats, with the averages of 797.7 and 749.5 g/kg, respectively, which contributed to about 6% more efficiency for total digestible nutrients.

CONCLUSION

Inactive dry yeast (Saccharomyces cerevisiae) can replace soybean meal in diets for Saanen goats with no changes on nutritive value of diets.

The primiparous goats are more efficient in the use of nutrients of diets than multiparous, in the postpartum period.